(19)

(11)

EP 1 159 639 A1

(12)

(43) Date of publication: 05.12.2001 Bulletin 2001/49 (21) Application number: 99952895.3 (22) Date of filing: 23.08.1999

(51) International Patent Classification (IPC)7: G01V 1/28 (86) International application number: PCT/US9919/168 (87) International publication number: WO 0055/647 (21.09.2000 Gazette 2000/38)

(84) Designated Contracting States: AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE Designated Extension States: AL LT LV MK RO SI (30) Priority: 15.03.1999 US 268261 (71) Applicant: PGS Data Processing, Inc. Houston, TX 77042 (US)	(72) Inventors: ALTAN, Suat Sugarland, TX 77479 (US) LI, Jianchao Houston, TX 77094 (US) ZHU, Xianhuai Sugarland, TX 77479 (US) (74) Representative: Skone James, Robert Edmund  GILL JENNINGS & EVERYBroadgate House7 Eldon Street London EC2M 7LH London EC2M 7LH (GB)